Call it yet another example of the consumerization of IT: the smartphone is now a leading tool of enterprise productivity.

Once upon a time, app stores were places where smartphone users went to get apps for tracking rush hour traffic, playing the occasional game, or finding animated guitar charts that would play when you strummed the screen.

Over the last four and a half years or so, however, smartphones have evolved into an invaluable business communications asset -- one that IT has some responsibility for -- thus raising the importance of app stores to businesses, according to a new report out this week.

However, despite the explosive popularity of Apple's (NASDAQ: AAPL) iPhone -- witness the excitement Tuesday when Apple rolled out the iPhone 4S, a relatively minor update -- virtually all smartphone providers also have app stores now.

Not far behind the consumer marketplace, app stores have also begun sprouting up inside many IT organizations or even the businesses themselves.

In fact, a new report by analyst firm Canalys predicts that "enterprise app stores will redefine channel IT business over the next three years" -- more so than even the cloud, the firm projects.